THYROGLOBULIN LEVEL HAS PROGNOSTIC ROLE

NEW YORK (Reuters Health) Jun 27 - Measurement of serum thyroglobulin (Tg) before radioiodine thyroid remnant ablation is an inexpensive way to identify patients with a particularly good prognosis, researchers say.

After resection for differentiated thyroid cancer, patients with low Tg levels were unlikely to have persistent or recurrent disease after ablation, in a new meta-analysis.

"Most people do not have recurrence, so there's always a question initially in terms of who is more likely to have a recurrence than someone else, and whether or not they need more aggressive treatment," Dr. Henry B. Burch of the Walter Reed National Military Medical Center in Bethesda, Maryland, one of the study's authors, told Reuters Health.

As reported online May 25 in the Journal of Clinical Endocrinology and Metabolism, Dr. Burch and his colleagues pooled data from 15 studies involving 3,947 patients with differentiated thyroid cancer (including some who were treated at their own center), to determine whether preablation Tg values had any association with patient outcomes.

Pre-ablation Tg cutoff values ranged from 3.2 to 30 ng/mL, but most studies used 10 ng/ml. Tg levels were below threshold for 70% of patients.

Follow-up averaged a least a year in all but one study, at least three years in eight studies, and more than 15 years in two studies.

Overall, below-threshold preablation Tg levels had a 94.2% negative predictive value for biochemical or structural evidence of disease during follow-up.

The negative predictive value was higher than 90% in all but two of the studies, the authors noted.

"Our study...clearly demonstrates that preablation Tg measurement has the potential to serve as a useful negative predictor of persistent and recurrent DTC," Dr. Burch and his team write. "Specifically, a patient with a postoperative preablation Tg value of less than 10 ng/ml has only a 6% likelihood of having persistent disease."

Additional measures would be needed, they add, to stratify risk in the group with low Tg values who did have persistent disease.

As for whether patients with low Tg values may be able to avoid additional treatment, the authors say more research is needed.

"All of the studies that we looked at, including our own data, ended up giving patients radioiodine and then following them," Dr. Burch told Reuters Health. "What's really needed is a randomized trial where you take patients who have a low preablation thyroglobulin and randomize half of them to receive the ablation and the other half not to, and then compare the outcomes in the two groups."